A Student on MICE Adam Dobbs, Imperial College Goldsmith’s Particle Physics Summer School 21 st July 2009

Outline 1.Why MICE? - a brief overview of the Standard Model - neutrino masses and oscillations - the neutrino factory and muon cooling 2.What is MICE? - muon ionisation cooling – what we hope to show - MICE design - schedule 3.Life on MICE (what I do) - the office - accelerator beam loss and MICE particle rate 4.Conclusion - where we’ve been - why I like what I do 21/07/20092A Student on MICE, A Dobbs

1. WHY MICE? Introduction to the Standard Model Neutrino masses and mixings The Neutrino Factory 21/07/20093A Student on MICE, A Dobbs

The Standard Model of Particle Physics A mathematical model of matter and forces at the most fundamental level currently known (with the notable exception of gravity) Extraordinarily good agreement with experiment Held good for the last 40 years... but not a “final theory” 21/07/2009A Student on MICE, A Dobbs4

“Fundamental” Particles 21/07/2009A Student on MICE, A Dobbs5 u Q = +2/3 m = 2.4 MeV s = 1/2 c Q = +2/3 m = 1.27 GeV s = 1/2 t Q = +2/3 m = GeV s = 1/2 d Q = -1/3 m = 4.8 MeV s = 1/2 s Q = -1/3 m = 104 MeV s = 1/2 b Q = -1/3 m = 4.2GeV s = 1/2 τ Q = -1 m = GeV s = 1/2 νeνe Q = 0 m < 2.2 eV s = 1/2 νµνµ Q = 0 m < 0.17 MeV s = 1/2 ντντ Q = 0 m < 15.5 MeV s = 1/2 µ Q = -1 m = MeV s = 1/2 e Q = -1 m = MeV s = 1/2 QuarksLeptons Fermions γ Q = 0 m = 0 s = 1 z0z0 Q = 0 m = 91.2 GeV s = 1 w±w± Q = ±1 m = 80.4 GeV s = 1 H Q = 0 m > 112 GeV s = 0 g Q = 0 m = 0 s = 1 Bosons EMWeakStrong Higgs G Q = 0 m = 0 s = 2 Gravity

Interactions 21/07/2009A Student on MICE, A Dobbs6 Image courtesy of Wikimedia Commons

Beyond the SM: Neutrino Mass and Mixing 21/07/2009A Student on MICE, A Dobbs7 SM had assumed neutrinos to have a zero mass First evidence against this came in 1960s when Ray Davis at the Homestake mine experiment observed a deficit in the number of solar neutrinos detected from that predicted by the standard solar model → “The Solar Neutrino Problem”

The Plot Thickens Missing neutrinos and the mysterious appearance of neutrinos were subsequently noticed in neutrinos generated by cosmic rays hitting the atmosphere (Super Kamiokande, SNO), in nuclear reactors (KamLAND) and in particle accelerators (K2K) What is the cause? 21/07/2009A Student on MICE, A Dobbs8 Inside Super Kamiokande, a 50,000 ton water Cherenkov detector based in the Mozumi Mine, Japan

Solution: Neutrino Oscillations 21/07/2009A Student on MICE, A Dobbs9 All the information about a quantum system is held in a mathematical entity known as the wavefunction, ψ Neutrino mass (eigen)states are not the same as neutrino weak flavour (eigen)states......but they are related its a questions of hats

The Mixing Matrix or How the hats are related 21/07/2009A Student on MICE, A Dobbs10 where,andare CP violating phases... yes... lets not think too hard about this... See “Where have all the neutrinos gone” on Thursday The Point: the neutrino weak force states are a combination of the neutrino mass states and we want to know exactly how by measuring the four parameters

Oscillations Graphically: Flavour = combination of masses 21/07/2009A Student on MICE, A Dobbs11 = + Consider 2 neutrino case for simplicity. When a neutrino has just been formed in a weak interaction the neutrino is in a pure single flavour state, which is a combination of two mass states:

Probing Oscillations: The Neutrino Factory The Neutrino Factory is a proposed next generation high intensity neutrino source Allow us to study the mixing parameters to greater precision Only one of various contenders for a next generation neutrino source... but probably the best (but probably the most difficult to realise too) 21/07/2009A Student on MICE, A Dobbs12

How does it work? Get a beam of protons and zap them into a target which generates pions which will then decay into muons... 21/07/2009A Student on MICE, A Dobbs13... which are put into a big storage ring until the muons decay to neutrinos! Feynman diagram for muon decay

What does it look like? 21/07/200914A Student on MICE, A Dobbs

OK, but what does all this have to do with small rodents? Once the muon beam has been generated from the pions it needs to be cooled, sort of shrunk, so that it will fit into the other NF components further downstream, before decaying into neutrinos Cooling becomes even more necessary when considering a future muon collider Conventional beam cooling using EM fields does not work because of the short muon life time Enter MICE... 21/07/2009A Student on MICE, A Dobbs15

2. WHAT IS MICE? Muon Ionisation Cooling MICE layout MICE Schedule 21/07/200916A Student on MICE, A Dobbs

A Little Accelerator Physics MICE stands for the International Muon Ionisation Cooling Experiment “Cooling” refers to the phase space compression or emittance reduction of the muon beam Phase space here refers to the normal position space x, y, z and the momentum space x’, y’, z’ of the beam of particles The emittance of a beam refers to how much volume a beam occupies in this phase space 21/07/2009A Student on MICE, A Dobbs17

Emittance 21/07/2009A Student on MICE, A Dobbs18 x x’ a b - the slope of the particle trajectory relative to the axis z x y Beam Real Space Part of Phase Space

Ionisation Cooling Pass the beam through an absorber e.g. liquid hydrogen, lithium hydride The particle beam ionises the medium, the beam particles losing energy and momentum in all directions Re-accelerate the beam in the beamline direction (z) only, using a radio frequency electric field Muon ionisation cooling has never been demonstrated before... but concept is simple 21/07/2009A Student on MICE, A Dobbs19 LiH 2 v v RF v

MICE Goals Produce a functional Neutrino Factory cooling channel (the factory itself will require multiple channels). Specifically: Produce an input muon beam of momentum between 140 to 240 MeV / c, and a tuneable emittance between 1 to 12 π mm rad Measure the emittance before and after cooling to a precision of 1 part in 1000 Produce an approximately 10% cooling effect 21/07/2009A Student on MICE, A Dobbs20

MICE Home Based in the UK at Rutherford Appleton Laboratory, Didcot Uses the ISIS 800MeV synchrotron accelerator as a proton source Possible site for the Neutrino Factory 21/07/2009A Student on MICE, A Dobbs21

21/07/2009A Student on MICE, A Dobbs22 ISIS MICE MICE Layout MICE TargetPion capture with Q1-3 D1 D2 Q4-6Q7-9 DS Tracker CKOV A, B D = Dipole bending magnet Q = Quadrupole magnet DS = Decay solenoid GVA1 = Scintillator counter CKOV = Cherenkov detector GVA1 Dipoles → bend the beam Quadrupoles → focus the beam

What it looks like 21/07/2009A Student on MICE, A Dobbs23

The Finished Product 21/07/2009A Student on MICE, A Dobbs24

MICE Aspirational Schedule 21/07/2009A Student on MICE, A Dobbs25

3. LIFE ON MICE The Office Beam Loss 21/07/200926A Student on MICE, A Dobbs

The Office 21/07/2009A Student on MICE, A Dobbs27 Arrive Sit here Use these Read this Scribble a bit Look for some interesting weather Go home

MICE in ISIS 21/07/2009A Student on MICE, A Dobbs28 MICE is an unique experiment on ISIS – the only one capable of disrupting the synchrotron The MICE target causes a measure of disruption to the ISIS beam and thus a possible increase in the radioactivity present MICE Everyone else

Beam Loss and Particle Rate In fact, the more beam loss we produce in ISIS, the more particles we get down the MICE beamline – something we badly need (our current particle rate is far too low) → a tension of needs exists As a result beam loss in ISIS must be monitored and studied in relation to the MICE target Part of what I do 21/07/2009A Student on MICE, A Dobbs29

Beam Loss Simulation: ORBIT ORBIT = Objective Ring Beam Injection & Tracking Particle tracking code used by ISIS to simulate their machine Built under C++ and SuperCode Free It has issues... 21/07/2009A Student on MICE, A Dobbs30

Short-Fat Target 21/07/2009A Student on MICE, A Dobbs31

Long-Thin Target 21/07/2009A Student on MICE, A Dobbs32

Cylindrical Target 21/07/2009A Student on MICE, A Dobbs33

Beam Loss Data Analysis 39 ionisation chamber beam loss monitors positioned around the ISIS ring Noisy data – use averages to extract signal Look for affects solely due to the MICE target - remove background signal due to normal ISIS beam loss Target position and dip time also recorded 21/07/2009A Student on MICE, A Dobbs34

The ISIS Spill and Beam Loss 21/07/2009A Student on MICE, A Dobbs35 Beam Intensity (V) Target Position (V) Total Beam Loss (V) Spill with MICE target present Spills without MICE target present

Beam Loss and 3 rd Order Polynomial Fit 21/07/2009A Student on MICE, A Dobbs36 Total Beam Loss (V) 3 rd order polynomial fit to MICE specific beam loss Losses due to beam injection Losses due to beam extraction

Data reduction: 1 point per dip 21/07/2009A Student on MICE, A Dobbs37

Its Useful Too: Target Melt Event 21/07/2009A Student on MICE, A Dobbs38 8mm Ti Melting Point = C

Beam Loss Vs Particle Rate 21/07/2009A Student on MICE, A Dobbs39

4. CONCLUSION Where we’ve been Why I like what I do 21/07/200940A Student on MICE, A Dobbs

Where We’ve Been Introduction to particle physics and the Standard Model Neutrino mass and oscillations The Neutrino Factory to further investigate oscillations MICE to demonstrate cooling needed for a NF MICE – what, when MICE and ISIS beam loss issues 21/07/2009A Student on MICE, A Dobbs41

Why I like what I do “Fill the earth and subdue it” - Genesis → Physics Physics is challenging, beautiful, useful and even fun If you still don’t like it, a physics degree equips you for many professions... and you don’t have to get up too early in the mornings 21/07/2009A Student on MICE, A Dobbs42

Thank you!

Masses = Combination of flavours 21/07/2009A Student on MICE, A Dobbs44 =+ =+ Flavour 1 components constructively interfere, flavour 2 components destructively, hence the neutrino is a pure flavour 1 state

Different masses travel at different speeds 21/07/2009A Student on MICE, A Dobbs45 Because the different mass states travel at different speeds, the phases between the two changes → flavour 1 components no longer interfere purely constructively, flavour 2 components no longer interfere purely destructively.

Relative amounts of each flavour component change with time 21/07/2009A Student on MICE, A Dobbs46 So our neutrino now has components of both flavour 1 and flavour 2. The amplitude of the wave for each flavour dictates the probabilty that when the neutrino is detected it will be observed as that flavour. The mixings angles dictate how these amplitudes vary over time.

KamLAND: Observation of Oscillation 21/07/2009A Student on MICE, A Dobbs47